I think it would be really hard to give effective C&C on the tree at this point, because in a scene mockup, you need to have a good idea of what an object is going to be placed against before critique will be at it's most effective. Until we know what the grass tiles will look like, or whether there wlil be dirt, water or building tiles included in the scene and how they will look like stylistically, any C&C given to the tree has the possibility of being nullified as each new tile is added.
I could give you enough C&C to turn your tree into something one would see in Seiken Densetsu3, but it would be useless if the rest of your tiles looked like something from Legend Of Zelda:Link to the Past